I have gone through a few canisters of
Perfect Food - Super Green Formula simply because it's the major brand available at my local health store.
Overall, I would recommend it or any similar "green drink" to anyone looking to improve their diet or compensate for a lack of vegetables. However, I don't buy into the whole alkaline thing Tony hails about. For one, and admittedly this is prejudiced, I'm never going to take diet advice from a motivational guru. If this whole acid/alkaline deal was as abundantly clear as Tony makes it out to be, I'd expect this diet to be more widely accepted and recommended by more health experts.
As far as results go, I never noticed anything significantly different after drinking 1-2 servings a day of this stuff. Your milage may vary, but I'd not expect to be transformed in the way Tony describes. Yet, I said I recommended it, didn't I? Well, cost-factors aside, it's clearly got some great nutritional value and it's filling and it doesn't taste toooo bad. (it's exactly as you'd expect liquid veggies to taste like. It's no Gatoraid, but it's not disgusting). I mixed mine with a scoop of whey protein and a scoop of Metamucil for my breakfast and sometimes snack or dinner. It's a pretty filling combo and probably comes in under 150 calories, which is super low for the nutrients it provides and how filling it is.
Final word: Read the labels, do some research, make a decision and try it out for yourself.